VRE is exploring expansion to Haymarket on the NS B-Line at current.
Expansion south to Bealeton is not on the current radar. Expansion south of Fridericksburg is also not on the immediate radar.
The reason is the way VRE is organized. It is owned/run by the various local jurisdictions that it serves (in the form of two regional transportation commissions made up of public servants from those jurisdictions), and it is also operationally funded by those jurisdictions (about 40-45% or operational costs). VRE is not, in any form, a State agency, and lacks the powers/funding such an agency would have.
In order to expand to new Jurisdictions, those Jurisdictions would have to join PRTC or NVTC (the two transportation commissions) and also offer funding as the existing Jurisdictions do. TZo date, Spotsy is very on the fense about doing so, and Faquier is not even that interested. Till they join, no expansion will occur in those directions.
In addition, as someone pointed out above, VRE is not a track owner, but is a "renter" in effect, and must negotiate with the host railroads for every inch of operation it offers. And put simply, it's not remotely as simple as many might like to think to get permission for expansion, of either service area, or number of trains.
Even to expand to Heymarket, huge sums of money would be required, to upgrade the B-Line to dual track, with additional signaling, grade crossing seperation, new stations, and a storage yard, etc, etc, etc. The cost of that is massive, and funding isn't just laying around.
If you want to see what they are looking it, it can be found in detail here:
http://www.vre.org/about/Gainesville-Haymarket.pdf